Features of Gas Exchange Surfaces (Cambridge (CIE) IGCSE Biology)
Revision Note
Written by: Lára Marie McIvor
Reviewed by: Lucy Kirkham
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Features of gas exchange surfaces
All gas exchange surfaces have features in common
These features maximise the rate of gas exchange taking place; they include:
Large surface area to allow faster diffusion of gases across the surface
Thin walls to ensure diffusion distances remain short
Good ventilation with air so that diffusion gradients can be maintained
Good blood supply to maintain a high concentration gradient so diffusion occurs faster
The alveolus is the gas exchange surface in humans
Examiner Tips and Tricks
You may notice that several of the features of alveoli that aid their function are the same as those that make villi, or root hair cells, suited to their function, e.g.
large surface area
good blood supply
steep concentration gradient
These structures are all examples of exchange surfaces; they allow the efficient movement of substances across their surface by diffusion, active transport and/or osmosis. So, if you learn the features of one exchange surface, you also know the features of the others!
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